Your question is a little hard to parse. Do you mean that you'd like to be able to insert some text at the beginning of several lines? Thus, from this:
A line of code or prose.
A second line text.
A third line.
INSERTED TEXT A line of code or text.
INSERTED TEXT A second line text.
INSERTED TEXT A third line.
If so, I usually deal with this by using the multi-cursor function: hold ctl+shift and arrow up or down to disperse cursors, then type your desired text; or, hold alt+super (on mac: option+command) and click and drag your mouse up the beginning of the rows (or click at the beginning of each line). The only time this method doesn't work so smoothly is when you're using text wrapping.
I imagine you could also write a snippet to do this with a few less clicks/presses.